Air conditioning



July 12 1938. B. OFFEN 2,123,742

AIR CONDITIONING Fi'led Dec, 8, 1950 2 Sheets-Shet 1 July 12, 1938. B.OFFEN 9 AIR CONDITIONING Filed Dec. 8, 1950 2 Sheets-Sheet 2 PatentedJuly 12, 1938 I UNITED srATas AIR ooum'rromno Bernard Oii'en, Chicago,Ill., assignor, by mesne assignments, to Carrler Corporation, Newark, N.J-., a corporation of Delaware Application December 8 ,1930, Serial No.500,716

11 Glalms. (Cl. 261-115) Y This invention relates to improvements in airconditioning, and more particularly to apparatus for controlling thetemperature conditions of air delivered into auditoriums, theatres, andspecial 5 purpose rooms in industrial plants.

The object of the invention is to provide a practical and efiiclentmethod of regulating the temperature of theconditioned air by thetemperature in the room or auditorium by controlling the volume of waterutilized, in the conditioning apparatus for cooling the air, bythermostatic means located in the conditioned room or auditorium.

In addition to the temperature, the humidity of the air is a factor inthe conditioning of air and therefore a further object of the inventionis to provide a dual control whereby both temperature and humidityconditions are maintained to afford the desired conditions of comfort.

' As well knownv in the art of air conditionin the amount of moisture inthe air, expressed in terms of relative humidity, has a marked effect onthe temperature to which the air may be heated to give the properconditions of bodily g5 comfort. Thus air containing a high percentageof moisture can be supplied at a lower temperature and vice versa, sothat the properconditioning of air is a matter of maintaining a certaindifferential between the temperature and humidity, as for instance asrecorded by wet or dry bulb thermometers. This differential, however, isnot constant but variable with the changes 'in the atmosphericconditions in the auditorium or other space being supplied. For example,a

crowded auditorium in cold weather demands a different conditioning, ofthe air supply than during warm or mild weather, or when partiallyfilled, so that regardless of exterior conditions and temperature, anyautomatic control of air conditioning system should properly be governedby the temperature within the space to which air is delivered. Thus thepresent disclosure depends not so muchon the units which make up the IReferring to Figure 1, the conditioning apparatus consists in general ofa chamber or housing I, having air inlet openings or ducts 2 and 3communicating at one end, and leading to a fan chambertat its other endthrough an inter- 5 mediate converging section 5. Within the. fanchamber is a fan 6 of asuitable suction type, driven by a motor "I andoperative to draw the air through the casing l and discharge it throughan outlet duct 8 into the auditorium through 10 smaller ducts andpassages.

The air entering the casing I through the openings or passages 2 and 3is admitted from two sources, viz., from the outer atmosphere and fromthe interior of the auditorium. Thus the 15 passage 2 is the fresh airinlet and the passage 3 the return or recirculated air inlet, the freshair being at the outside temperature and the return air at the insidetemperature, and which vary according to the climate and season of theyear. 20 Sets of dampers 9 and It are located in these fresh air andreturn air passages respectively, and these are thermostaticallyoperated to regulate the proportion of each source of air, as will laterbe described in detail.

Within the casing lare'located the several air treating elements of thesystem, which, considered as a unitary assembly, is termed thedehumidifier. Broadly defined, a dehumidifier may be any cooling surfaceor medium into which the 30 incoming air comes into contact, so that 'acooling effect is produced. Thus a water spray or refrigerated coils mayserve as a dehumidifier, although I prefer to employ a combination ofthe two, and control the degree of dehumidifying v and consequently thetemperature by regulating automatically the amount of water issuing fromthe spray heads. Thus in the central portion of the casing i are threevertical banks of refrigerranged in' pairs, one pair to acoil, each pair5 being connected together, exterior to one side of the casing and witha branch'supply pipe l3,

leading to a main supply pipe M from a pump l5, driven by a motor M. Ineach of the branch supply pipes I 3 is a valve it of the diaphragm orother suitable type, the same being operated by bellows units ll, aswill hereafter be described.

Immediately beyond the refrigerating coils is anotherpair' oftransverseheaders l8, it, one

near the top and the other near the bottom of the casing, the same beingconnected at intervals across the casing by vertical pipes or risers l9having spray heads l9 mounted at intervals therealong and directedtoward the refrigerated coils The top header is also provided with sprayheads l8 located between the risers and directed in a downwardlydirection. A branch supply pipe 20 leads from the main supply pipe l4,and located in this branch pipe is a threeway valve 2|, also operatedand controlled by a bellows unit 22. A second branch pipe 23 from thethree-way valve 2| enters the casing and empties into a shallowreceptacle or pan 24 in the bottom of the casing and extending beneaththe area within the range of the spray heads.

.This receptacle collects the water discharged from the several sets ofspray heads, and the water therein is recirculated through a return pipe25 leading from the receptacle to the suction side of the pump l5.

Beyond the bank of vertical spray pipes I9 is the air cleaning elementconsisting of a vertical bank 26 of zig-zag plates spaced at shortdistances apart and. thus forming a multiplicity of circuitous passagesthrough which the air is drawn. The surface of this bank of plates iscontinually sprayed with water which is supplied through a header 21extending across the upper portion of the casing, and provided with aseries of nozzles 2| which direct streams of water into the passagesbetween tne plates. This header is also supplied with water from thepump through a branch pipe 28 from the main supply pipe H. The functionof the air-cleaning element is to remove the impurities from the air,suchas particles of dust and dirt which impinge against the wet surfaceof the zig-zag plates and are retained and eventually washed down intothe receptacle below. The air cleaner is not essentially a part of thedehumidifying. apparatus, and therefore functions continuously andsteadily while the systein is in operation.

' Referring now to the control mechanism, it will be observed that thesupply of water to the spray heads is controlled by the valves l5, andthey in turn by the bellows l1 and 22, the same being of any suitabletype and design operating by variations of air pressure to open andclose the valves. The air pressure to these bellows units is suppliedthrough an arrangement of piping connected with a suitable compressorunit whereby a pressure of, say 15 pounds is maintained. Thus a main airsupply pipe, is connected in parallel with all of the bellows units l1and 22 through short branch pipes 30', so that all of them operate inunison to increase or decrease the supply of water admitted throughtheir respective valves to the several spray heads.

The air pressure in the pipe 30 leading to the pressure-controlledvalves is thermostatically controlled by the following arrangement ofthermostats and connecting air pipes: Since it is the purpose toregulate the temperature of the air primarily by that in the auditorium,a thermostat 3| is located in the return air duct 3 from the auditorium,it being manifest that the perature-responsive element operating a valvewhich in turn controls the air admitted to a feed pipe 32 under pressurefrom its source. Now this feed pipe 32 in my preferred arrangement doesnot connect directly with the pipe 30 leading to the bellows-operatedvalves IE, but rather is connected indirectly through a thermostat 33located in the discharge duct 8 leading to the auditorium and thereforeon the opposite side of the dehumidifying apparatus. Adjacent thethermostat 33 is another thermostat 34 having a temperature-responsiveelement which is the equivalent of a dry bulb thermometer and thusregisters the actual temperature, whereas the heat-responsive element ofthe thermostat 33 is the equivalent of a wet bulb thermometer whichregisters a slightly lower temperature, depending on the relativehumidity of the air. Thus between the wet and dry bulb temperaturesthere is a diiferential of charged will have a certain relative humiditypredetermined as conducive to maximum comfort in the room beingsupplied.

Now, bearing in mind that a change in the volume of spray waterdischarged into the dehumidifier will influence both the temperature andrelative humidity of the air discharged, it follows that to maintain aconstant relative humidity, the volume of the spray water must becontrolled by both the thermostat 3| in the return air passage and alsoby the wet bulb thermostat 33 in the discharge duct.

Thus as shown in Figure 1, the wet bulb thermostat 33 directly controlsthe air pressure in pipe 30 leading to the bellows-actuatedvalves ll inthe water supply pipes l3, while the thermostat 3| in the return airduct acts in an auxiliary caforth.

Now the wet bulb thermostat 33 may be considered as consisting of abellows or other pneumatically-expansible unit which is operativelyconnected with a valve controlling the air pressure admitted to the pipe30 through an air supply pipe 35, the bellows being so arranged as toadmit air to regulate the valves |6 on the water supply pipes as long asthe temperature of the conditionedair conforms to the setting of the wetbulb thermostat. It will be noted, however, that the pipe 32 from thethermostat 3| in the return duct 3 leads to the wet bulb thermostat andadmits air under pressure to oppose the action of the bellows at thenormal operating temperature, and similarly that a pipe 36 from the drybulb thermostat 34 is connected in parallel with the pipe 32 from thethermostat 3|, and likewise acts to pass or admit air under pressure tocounter-balance or augment the air pres- 4 sure from thermostat 3|. Thusit will appear that the control of the spray water is through the mediumof the three thermostats 3|, 33, and 34 acting in conjunction with eachother.

As already pointed out, the wet bulb thermostat 33is in immediatecontrol of the valves to the water sprays, but its operation iscontrolled by the other two thermostats acting together or singly,depending on the difference in the temperature of the air in theauditorium and that being supplied thereto.

Explaining the operation of the system with its temperature and humiditycontrol, it is manifest that as the air is drawn into the casing Ithrough the fresh air and return passages 2 and 3, the warm air at, say,75 being tempered by the fresh air and the entire volume of incoming airpassing through the refrigerating coils and thereby cooled. Now theamount of heat transference or cooling of the air is regulated by the*volume of water that is being sprayed, and further by the actualcontact between the air and the water in finely divided form, thiscooling effect varying directly 'as the volume of water sprayed from theheaders it, as well as that sprayed laterally from the vertical risersiii.

The cooling of the air also results in a reduction of the moisturecontent as a portion is condensed, so that as the air leaves thedehumidifier it is at a lower temperature and has a lower moisturecontent than when it entered.

In this connection it is important to bring out thedistinction betweencooling the air and the dehumidification of the air by the water or anyother cooling medium. In'the first place, the air will be cooledwhenever the temperature of the water cooling medium is lower than thatof the air, while the amount of cooling, i. e., the heat extracted fromthe air will be proportional to the area of the cooling medium availablefor contact with the air, which in the present disclosure is representedby the volume of water that is being sprayed into the chamber at anygiven moment. Dehumidification on the other hand is the removal ofmoisture from the air by condensation, and involves the cooling of theair below its saturation temperature. Thus while cooling anddehumidifying both involve an interchange of heat, the latter brings inanother factor, namely, the saturation or dew point of the air, that is,the temperature at which the air is saturated with moisture. As aconsequence, therefore, the air may be treated without altering itstemperature or its relative humidity, or it can be reduced to asaturation point of any predetermined temperature, and further can beconditioned and delivered in any desired relationship between the drybulb, the wet bulb and saturation temperatures, by the setting of theseveral thermostatic devices, so that theair on being discharged intothe room will, when mixed with the air already in the room, produce thedesired degree of comfort.

Thus it will be seen that if the air is to be discharged into the roomat the temperature to be determined by that existing in the room of say,75 (which is the setting of the thermostat 3i), and at the same time tobe maintained at a constant relative humidity, the difierence betweenthe temperatures of the wet and dry bulb thermostats 33 and 34 must bekept practically constant. Accordingly, if it is assumed that the wetbulb thermostat is set at 65 and the dry bulb thermostat at 70, thecondition of the air entering the system may vary, so that the'dry bulbtemperature rises to say, 73. This increase would actuate the dry bulbthermostat so as to admit air pressure through the pipe 35 to the wetbulb thermostat and thus increase the temperature setting thereof to158, or 3 higher than normal, in order to maintain the same difierentialand therefore the same relative humidity in the air discharged into theroom. In other words, the wet bulb thermostat would not function to varythe volume of spray water until the wet bulb temperature reached 68instead of 65. But the air at 73 is too high to maintain the room at anormal temperature of 75, so con sequently the temperature of the returnair would be increased and the thermostat 3| would accordingly operateto vary the setting of the wet bulb thermostat, so that the actual ornet change in the volume of spray water is an increase in such amount asto lower the dry bulb temperature of the discharged air and yet maintainthe air. at the given relative humidity. In short, the three thermostatscounteract each others action in such a way as to maintain a balancedcondition of temperature and relative humidity in the system at alltimes, this being accomplished entirely by regulating the amount ofwater spray and consequently the cooling effect on the air.

From the foregoing, it will be seen that the thermostat 3! is theinstrument in primary control of the system, since it responds totemperature changes in the auditorium, and in so doing governs thesetting of wet bulb thermostat 33- which in turn directly controls thewater supply to the spray head in the dehumidifying chamber. .Thus, forexample, assuming a condition of 50% occupancy of the auditorium at atemperature of 75, a further increase in occupancy would be accompaniedwith an increase in temperature due to greater bodily heat given off.Now, thermostat 3! would react to this rise in temperature and wouldpass air pressure through pipe 32 to thermostat 33 to change its normalsetting from 65 to 68 as before stated, with the result that more waterwould be supplied to-the sprays to increase the cooling eifect and thuslower the temperature of the air, at-the same time dehumidifying more ofthe air. This air is then discharged into the auditorium to compensatefor the rise in temperature therein.

Thus it will be seen that the action of ther-- mostat 3| on thermostat33 is to increase or decrease its normal setting, and assuming the drybulb temperature remained the same, it follows that the diiferentialwould vary with temperature changes in the auditorium. But the objectssought is to keep the differential constant and this is the function ofthe dry bulb thermostat 3 If this thermostat 34 is set at 70 as in theexample given, an increase in the wet bulb temperature to 68 means alesser differential, and consequently a more humid condition of the air,for the less the differential the more nearly the air approaches asaturated condition. But the dry bulb thermostats automatically correctthis condition by passing air from pipe 35 and through pipe 36 connectedwith pipe 32 leading from thermostat 3|, to control the efiect of thelatter on the setting of the wet bulb thermostat 33, so that thedifferential remains constant, although the limits of the wet and drybulb temperatures may vary. In short, the purpose of the wet and drybulb thermostats 33 and 34 essentially act as a check on the thermostat3i to insure against the delivery of saturated air into the auditorium.

It may be explained at this point that for some types of installationsthe percentage of moisture in the air is not an important factor, andtherefore the wet and dry bulb thermostats may be omitted and the volumeof water spray controlled entirely by the .thermostat 3| in the room orreturn air duct. In other words, the air pipe 32 from thermostat 3|would be connected directly with the pipe and thus control the operationof the spray water valves I6 direct.

While this is a simpler arrangement, it nevertheless embodies the sameprinciple of control, namely, that of regulating the temperature in theroom by controlling the volume of water supplied to the dehumidifierfrom a thermostat located in the room or in the return air duct from theroom.

To complete the system requires the automatic control of the dampers 9and iii in the fresh air and return air passages 2 and 3 to the casingI, this being accomplished by means of thermostats 31 and 38 located inthe two passages respectively.

These thermostats control air-actuated bellows units 39 and 40,connected with the dampers in their respective air passages, and are setto function throughout a given range of, temperature. Thus if theoutside temperature falls, the thermostatically-controlled unit 39closes the damper 9 in the fresh air intake passage and the unit 40opens the damper 10 in the return air passage, so that a greaterproportion of the warm inside air to cold outside air enters thedehumidifier. This part of the apparatus, however, iscommonly used andtherefore is disclosed only for the purpose of showing the completesystem.

Having set forth a preferred embodiment of my invention,

I claim:

1. In an air conditioning apparatus, the combination of a casing throughwhich the air to be conditioned is circulated, cooling coils mounted insaid casing, means for spraying water including a supply pipe, apressure-actuated valve in said supply pipe, a thermostat responsive tothe temperature in the room to which the conditioned air is delivered,and a thermostat responsive to the wet bulb temperature of airdischarged from said casing, said thermostats being inter-connected toregulate said water supply valve and thereby control the temperature andrelative humidity of the discharged air according to the temperatureconditions in the room.

' 2. In an air conditioning apparatus, the combination of a casingthrough which the air to be conditioned is circulated, cooling coilsmounted in said casing, means for spraying water including a supplypipe, a pressure-actuated valve in said supply pipe, a pair ofthermostats located in the delivery end of the casing, one responsive tothe wet bulb temperature and the other to the. dry bulb temperature ofthe air delivered to the room being supplied, and a thermostatresponsive to the temperature in said room, said thermostats acting inconjunction to control the volume of spray water and thereby therelative humidity and temperature of the air delivered to said room.

3. In an air conditioning apparatus, the combination of a casing throughwhich the air to be conditioned is circulated, cooling coils mounted insaid casing, a circulating spray water system, and means forautomatically controlling the volume of water sprayed, comprising apressure-actuated valve in said supply pipe, a pair of thermostatslocated in the delivery end of the casing, one responsive to the wetbulb temperature and the other to the dry bulb temperature of the airdelivered to the room being supplied, and a thermostat responsive to thetemperature in said room,

said wet bulb thermostat directly controlling said water supply valveand said dry bulb thermostat and room thermostat acting indirectly tocontrol the setting of said wet bulb thermostat, whereby the air isdelivered to the room at a constant relative humidity and at thetemperature determined by said room thermostat.

4. In an air conditioning apparatus, the combination of a casing throughwhich air to be con-' ditioned is circulated, cooling coils mounted insaid casing, means for spraying water including a supply pipe having avalve therein, pneumatic valveactuating means including' an air pressuresupply line, a pair of thermostats located in the delivery end of saidcasing, one being normally set to respond to a predetermined wet bulbtemperature and the other to a predetermined dry bulb temperature of theair, thereby establishing a fixed temperature differential correspondingto a predetermined relative humidity, said wet bulb thermostat directlycontrolling said air pressure line to said supply valve-actuating means,and said dry bulb thermostat having an auxiliary air connection therebyto increase or decrease the setting thereof with corresponding changesin the dry bulb temperature, and a thermostat in the room and alsoconnected with said wet bulb thermostat by an air pressure line andadapted to indirectly control the setting thereof by the temperature inthe room.

5. In an air conditioning apparatus, the combi-' nation-of a casingthrough which air to be conditioned is circulated, cooling coils mountedin said casing, means for spraying water including a supply pipe havinga valve therein, pneumatic valve-actuating means including an air supplyline, a thermostat located in the delivery end of said casing forcontrolling the air pressure in said .air line and responsive to the wetbulb temperature of the air, a thermostat located adjacent said wet bulbthermostat and responsive to the dry bulb temperature of the air, saidthermostats being normally set to a predetermined temperaturedifferential corresponding to a desired relative humidity, said dry bulbthermostat being connected by an auxiliary air pressure line to said wetbulb thermostat and operative to increase or decrease the settingthereof with corresponding changes in the dry bulb temperature, and athermostat in the room and also connected with said wet bulb thermostatby an auxiliaryair pressure line and operative to indirectly control thesetting thereof by the temperature in the room.

6. In an air conditioning apparatus, the combination of a casing throughwhich the air to be.

condiitoned is conducted, air cooling means within said casing includinga water spraying device and water supply pipe, a pressure actuated valvein said supply pipe, a temperature responsiv'e device on the inlet sideof said casing and co-acting wet and dry temperature responsive deviceson the discharge side of said casing, said devices being interconnectedto control the volume of water delivered to said'spraying device.

7. In an air conditioning apparatus, the com bination of a casingthrough which air to be conditioned is circulated, air cooling devicesin said casing comprising cooling coils and water spraying elements, awater supply pipe connected with said spraying elements, a valve in saidsupply pipe, pressure-regulated means for operating said valve includinginterconnected thermostatically actuated devices responsive to thecondition of the air entering and leaving said casing, and operating tocontrol the temperature and 'relative humidity of the air by the volumeof water sprayed over said coils.

8. A method of conditioning air, consisting of passing all of the air tobe conditioned through a chamber in which a cooling medium is locatedand controlling the temperature and/or relative humidity of the air byvarying the area of said cooling medium exposed to contact with the airthrough the medium of inter-connected thermostats responsive to thetemperature of the air' before entering, and the wet and dry bulbtemperatures of the air after leaving said chamber. 9. The method ofcooling and dehumidifying a quantity of air which comprises moving theair through an unobstructed passageway, subjecting the entire volume ofair in such stream to the action of a cooling medium in the form ofsegregated liquid particles in such manner that some of the air in thestreamvis cooled to a temperature below its dew point and moisture iscondensed therefrom while other portions of said air are cooled to alesser extent, the total cooling eflect being insufficient to bring theaverage air stream temperature down to the saturation value, and varyingthe degree of dehumidification obtained by varying the surface area ofsaid segregated liquid particles while in heat-exchanging relation withsaid air stream.

10. The method of cooling and dehumidifying a quantity of air'whichcomprises propelling the air in a single stream through an unobstructedpassageway, projecting a liquid at a temperature below the dew point ofthe air stream across said air stream in the form of a curtain ofsegregated liquid particles in such manner as to cool a portion of theair in such stream to a temperature below its dew point while coolingother portions of said air to a temperature above its dew point wherebyheat is extracted from portions of said air as latent heat ofcondensation and from other portions of said air as sensible heat andvarying the quantity of heat extracted as latent heat of condensation byadjusting said sprays to alter the surface area of the liquid particlesin heat-exchanging relation with said air stream.

11. In an air conditioning system, the combi nation with the enclosurein which conditioned air is used, of a conduit of undivided crosssection, means for propelling a single stream of air co-extensive withsaid conduit through said conduit into said enclosure, aseries of liquidsprays extending across the top of said conduit, means for supplyingsaid sprays with liquid at a temperature below the dew point of the airin said stream, said sprays being designed to discharge the liquidtherefrom in streams of liquid particles, and means for adjusting saidsprays to vary the surface area of the liquid particles inheat-exchanging relation with the air in said stream to thereby vary theproportion of the air whose temperature is reduced below its dew point.

BERNARD OFFEN.

